Ultrasonic‐Responsive Mechanoluminescence and Non‐Destructive Stress Sensing Enabled by Microstrain

Conventional mechanoluminescent materials are typically designed to respond to direct mechanical contact such as compression, friction, or destructive fracture, which leads to irreversible damage and limits repetitive testing. Ultrasound‐induced luminescence (USL) offers a non‐contact, non‐destructive excitation method with deep tissue penetration and minimal material damage. In this work, we report the systematic investigation of LiTaO 3 :Tb 3+ as an efficient USL material. Under ultrasonic excitation, the material exhibits bright green emission centered at ∼550 nm, corresponding to the characteristic transitions of Tb 3+ ions. The USL intensity shows a linear dependence on ultrasonic power and correlates strongly with the microstrain generated in the material. Through thermoluminescence analysis and density functional theory calculations, three distinct trap levels were identified in LiTaO 3 :Tb 3+ : shallow traps (I, 0.56 eV) responsible for afterglow, and deeper traps (II, 0.97 eV; III, 1.40 eV) that govern the stable USL emission. Furthermore, we demonstrate the potential of LiTaO 3 :Tb 3+ for ultrasound sensing applications by inserting different intervening media (pork, acrylic, aluminum alloy). The USL intensity and microstrain exhibit consistent correlations with ultrasonic power, establishing a three‐way relationship that can be used to characterize different materials. This work provides new insights into the mechanism of USL and opens avenues for non‐destructive stress sensing.